Vehicles, e.g., automobiles, generally have four wheels; i.e., two front wheels and two rear wheels, and can have an electronic control device for driving the wheels.
Japanese Laid-Open Patent Application (JP-A) No. 2006-256605 discloses a four-wheel-drive electronic control unit (4WD-ECU) as such an electronic control device. The 4WD-ECU disclosed in JP 2006-256605 A together with a vehicle stability assist (VSA)-ECU controls the drive force that acts on the vehicle; and, specifically, sets the four-wheel-drive force in terms of units of, e.g., torque.
A 4WD-ECU thus operates in coordination with the VSA-ECU and controls the drive force. Specifically, the VSA-ECU can request the 4WD-ECU to limit the drive force in the case that, e.g., the vehicle is traveling in an unstable state. The 4WD-ECU can reduce the drive force and improve vehicle stability in response to a request from the VSA-ECU.
A VSA-ECU or other vehicle behavior control means can generally be provided with at least one function from among a function for suppressing spinning of the wheels (traction control system), a function for suppressing locking of the wheels (antilock brake system), and a function for suppressing lateral sliding of a vehicle.